Question

According to recent estimates, the Milky Way galaxy contains about 400 billion stars. Which of the following is 400 billion expressed in scientific notation?

1) 4 x 10^14
2) 4 x 10^13
3) 4 x 10^12
4) 4 x 10^11
5) 4 x 10^10

Answer 1

400 billion is expressed as 4 x 10^11 in scientific notation, with the decimal moved 11 places to the left from the end.

Step-by-step explanation:

The student has asked how to express the number 400 billion in scientific notation. To convert this number to scientific notation, we move the decimal place until we have a number between 1 and 10, and then count how many places we moved the decimal. For 400 billion, or 400,000,000,000, we move the decimal place 11 spots to the left to get 4.0, and then express the number of moves as the exponent to base 10. So, 400 billion expressed in scientific notation is 4 x 10^11, which corresponds to the fourth option in the list.